Merge pull request #8852 from flox/tomberek.absolute.attrpath.notation

Absolute attrPath notation ("flakeref#.attrPath")

doc/manual/src/release-notes/rl-next.md

@@ -5,3 +5,5 @@
 - [Path-like flake references](@docroot@/command-ref/new-cli/nix3-flake.md#path-like-syntax) now accept arbitrary unicode characters (except `#` and `?`).
 
 - The experimental feature `repl-flake` is no longer needed, as its functionality is now part of the `flakes` experimental feature. To get the previous behavior, use the `--file/--expr` flags accordingly.
+
+- Introduce new flake installable syntax `flakeref#.attrPath` where the "." prefix denotes no searching of default attribute prefixes like `packages.<SYSTEM>` or `legacyPackages.<SYSTEM>`.

src/libcmd/installable-flake.cc

@@ -28,6 +28,11 @@ namespace nix {
 std::vector<std::string> InstallableFlake::getActualAttrPaths()
 {
     std::vector<std::string> res;
+    if (attrPaths.size() == 1 && attrPaths.front().starts_with(".")){
+        attrPaths.front().erase(0,1);
+        res.push_back(attrPaths.front());
+        return res;
+    }
 
     for (auto & prefix : prefixes)
         res.push_back(prefix + *attrPaths.begin());

src/libcmd/installables.cc

@@ -301,6 +301,11 @@ void completeFlakeRefWithFragment(
             completionType = ctAttrs;
 
             auto fragment = prefix.substr(hash + 1);
+            std::string prefixRoot = "";
+            if (fragment.starts_with(".")){
+                fragment = fragment.substr(1);
+                prefixRoot = ".";
+            }
             auto flakeRefS = std::string(prefix.substr(0, hash));
             auto flakeRef = parseFlakeRef(expandTilde(flakeRefS), absPath("."));
 
@@ -309,6 +314,9 @@ void completeFlakeRefWithFragment(
 
             auto root = evalCache->getRoot();
 
+            if (prefixRoot == "."){
+                attrPathPrefixes.clear();
+            }
             /* Complete 'fragment' relative to all the
                attrpath prefixes as well as the root of the
                flake. */
@@ -333,7 +341,7 @@ void completeFlakeRefWithFragment(
                         auto attrPath2 = (*attr)->getAttrPath(attr2);
                         /* Strip the attrpath prefix. */
                         attrPath2.erase(attrPath2.begin(), attrPath2.begin() + attrPathPrefix.size());
-                        completions->add(flakeRefS + "#" + concatStringsSep(".", evalState->symbols.resolve(attrPath2)));
+                        completions->add(flakeRefS + "#" + prefixRoot + concatStringsSep(".", evalState->symbols.resolve(attrPath2)));
                     }
                 }
             }
@@ -344,7 +352,7 @@ void completeFlakeRefWithFragment(
                 for (auto & attrPath : defaultFlakeAttrPaths) {
                     auto attr = root->findAlongAttrPath(parseAttrPath(*evalState, attrPath));
                     if (!attr) continue;
-                    completions->add(flakeRefS + "#");
+                    completions->add(flakeRefS + "#" + prefixRoot);
                 }
             }
         }

src/nix/nix.md

@@ -132,6 +132,8 @@ subcommands, these are `packages.`*system*,
 attributes `packages.x86_64-linux.hello`,
 `legacyPackages.x86_64-linux.hello` and `hello`.
 
+If *attrpath* begins with `.` then no prefixes or defaults are attempted. This allows the form *flakeref*[`#.`*attrpath*], such as `github:NixOS/nixpkgs#.lib.fakeSha256` to avoid a search of `packages.*system*.lib.fakeSha256`
+
 ### Store path
 
 Example: `/nix/store/v5sv61sszx301i0x6xysaqzla09nksnd-hello-2.10`

tests/flakes/absolute-attr-paths.sh

@@ -0,0 +1,17 @@
+source ./common.sh
+
+flake1Dir=$TEST_ROOT/flake1
+
+mkdir -p $flake1Dir
+cat > $flake1Dir/flake.nix <<EOF
+{
+    outputs = { self }: {
+        x = 1;
+        packages.$system.x = 2;
+    };
+}
+EOF
+
+[ "$(nix eval --impure --json $flake1Dir#.x)" -eq 1 ]
+[ "$(nix eval --impure --json $flake1Dir#x)" -eq 2 ]
+[ "$(nix eval --impure --json $flake1Dir#.packages.$system.x)" -eq 2 ]

tests/local.mk

@@ -12,6 +12,7 @@ nix_tests = \
   flakes/check.sh \
   flakes/unlocked-override.sh \
   flakes/absolute-paths.sh \
+  flakes/absolute-attr-paths.sh \
   flakes/build-paths.sh \
   flakes/flake-in-submodule.sh \
   gc.sh \